The present invention relates to telecommunications in general, and, more particularly, to a technique for forwarding a wireless telecommunications call across a regional or political boundary.
FIG. 1 depicts a schematic diagram of a portion of a typical wireless telecommunications system in the prior art, which system provides wireless telecommunications service to a number of wireless terminals (e.g., wireless terminals 101-1 through 101-3) that are situated within a geographic area. The heart of a typical wireless telecommunications system is Wireless Switching Center (xe2x80x9cWSCxe2x80x9d) 120, which is sometimes also known as a Mobile Switching Center (xe2x80x9cMSCxe2x80x9d) or a Mobile Telephone Switching Office (xe2x80x9cMTSOxe2x80x9d). Typically, Wireless Switching Center 120 is connected to a plurality of base stations (e.g., base stations 103-1 through 103-5) that are dispersed throughout the geographic area serviced by the system and to the local and long-distance telephone and data networks (e.g., local-office 130, local-office 138 and toll-office 140). Wireless Switching Center 120 is responsible for, among other things, establishing and maintaining calls between wireless terminals and between a wireless terminal and a wireline terminal (e.g., wireline terminal 150), which is connected to the system via the local and/or long-distance networks.
The geographic area serviced by a wireless telecommunications system is partitioned into a number of spatially distinct areas called xe2x80x9ccells.xe2x80x9d As depicted in FIG. 1, each cell is schematically represented by a hexagon; in practice, however, each cell usually has an irregular shape that depends on the topography of the terrain serviced by the system. Typically, each cell contains a base station, which comprises the radios and antennas that the base station uses to communicate with the wireless terminals in that cell and also comprises the transmission equipment that the base station uses to communicate with Wireless Switching Center 120.
For example, when wireless terminal 101-1 desires to communicate with wireless terminal 101-2, wireless terminal 101-1 transmits the desired information to base station 103-1, which relays the information to Wireless Switching Center 120 over wireline 102-1. Upon receipt of the information, and with the knowledge that it is intended for wireless terminal 101-2, Wireless Switching Center 120 then returns the information back to base station 103-1 over wireline 102-1, which relays the information, via radio, to wireless terminal 101-2.
Because a wireless terminal is mobile, it can be served by different base stations as it moves. In fact, if a wireless terminal moves a substantial distance it can be serviced by another wireless switching center and its satellite base stations rather than by the wireless terminal""s xe2x80x9chomexe2x80x9d wireless switching center. Furthermore, if the serving wireless switching center is in a different region or country than the wireless terminal""s home wireless switching center, this can cause the serving wireless switching center to fail to provide the correct service to the wireless terminal.
For example, FIG. 2 depicts a flowchart of a method in the prior art, which involves the interaction of two wireless switching centers (originating WSC 211 and serving WSC 213), home location register 212, and two wireless terminals (wireless terminal 201 and wireless terminal 202) as the wireless switching centers and home location register 212 attempt to establish a call from wireless terminal 201 to wireless terminal 202.
Originating WSC 211 and serving WSC 213 are each conventional wireless switching centers. Typically, home location register 212 and serving WSC 213 are in different regions (or countries) and serving WSC 213 and wireless terminal 202 are in the same region (or country). For example, home location register 212 might be in northern Illinois and serving WSC 213 and wireless terminal 202 might be in Seoul, Korea. It is irrelevant whether originating WSC 211 is in the same region (or country) as either home location register 212 or serving WSC 213. Home location register 212, might be, but is not necessarily, associated with originating WSC 211.
For the purposes of this specification, the word xe2x80x9cregionxe2x80x9d is defined as one or more geographic areas that are: (1) owned or operated by the same entity, or (2) administered by the same regulatory body. For the purposes of this specification, the word xe2x80x9ccountryxe2x80x9d is defined as a primary political unit (e.g., the United States, Canada, the United Kingdom, Japan, etc.) or a subprimary political unit (e.g., New Jersey, Alberta, Wales, Okinawa, etc.).
Wireless terminal 201 is typically a conventional wireless terminal that is currently served by originating WSC 211. It is irrelevant whether wireless terminal 201 is being served by its home wireless switching center or is roaming and being served by another wireless switching center.
Wireless terminal 202 is typically a conventional wireless terminal whose home location register is home location register 212. Home location register 212 comprises a database that includes:
i. the identity of the wireless switching center that is serving wireless terminal 202 at any given time (in this case serving wireless switching center 213); and
ii. at least one forward-to number for wireless terminal 202, which forward-to number might or might not include a xe2x80x9ccountry-codexe2x80x9d or international dialing prefix.
For the purpose of this specification, a xe2x80x9cforward-to numberxe2x80x9d for a wireless terminal is defined as the number to which an incoming call to the wireless terminal is forwarded if, for some reason, the incoming call cannot be completed to the wireless terminal. Typically, the forward-to number is associated with an answering machine.
As shown in FIG. 2, wireless terminal 202 is roaming and is currently being served by serving WSC 213. When wireless terminal 202 first enters the area served by serving WSC 213, wireless terminal 202 registers with serving WSC 213, and serving WSC 213 sends a message to home location register 212 indicating that wireless terminal 202 is currently being served by serving WSC 213. By sending a message to home location register 212 indicating that wireless terminal 202 is currently being served by serving WSC 213, serving WSC 213 enables home location register 212 to know where wireless terminal 202 is at any moment.
In steps 221 through 227 originating WSC 211, home location register 212 and serving WSC 213 attempt to set-up a call to wireless terminal 202. But if wireless terminal 202 is unavailable to receive the call, for any reason, serving WSC 213 seeks, in steps 228 and 229, a xe2x80x9cforward-toxe2x80x9d number from home location register 212 where the call can be forwarded. Such a number might represent an automatic answering system. But where home location register 212 and serving WSC 213 are in different regions (or countries), the forward-to number provided to serving WSC 213 might or might not have the proper international country code prefix and might be erroneously forwarded by serving WSC 213 as an national call, or might be erroneously forwarded as an international call. Furthermore, if the forward-to number is provided as a national number without an international country code prefix, but is to be associated with a another nation, then serving WSC 213 cannot complete the call properly.
Therefore, the need exists for a technique for properly forwarding calls for wireless terminals that are roaming across regional and political boundaries.
Some embodiments of the present invention are capable of forwarding a call properly for a wireless terminal when the wireless terminal is roaming in a different region (or country) than where its home location register resides. In particular, this is accomplished by having the home location register and the serving wireless switching system implement procedures for internationalizing, when appropriate, forward-to numbers, and for nationalizing, when appropriate the same forward-to numbers.
The illustrative embodiment of the present invention comprises: receiving at a home location register a transfer number request message from a serving wireless switching center, wherein the transfer number request message is associated with a wireless terminal; adding a country code associated with the home location register to a forward-to number associated with the wireless terminal when the forward-to number lacks a country code; and transmitting from the home location register the forward-to number to the serving wireless switching center.